Background: To investigate the value of post-induction chemotherapy (IC) cell-free Epstein-Barr virus DNA (cfEBV DNApostIC) for prognostication in locally advanced nasopharyngeal carcinoma (LA-NPC).
Methods: A total of 910 histologically proven LA-NPC undergoing radical IC + concurrent chemo-radiotherapy (CCRT) or targeted radiotherapy (CTRT) or both (CTCRT) were involved. The concentration of cfEBV DNA was measured by quantitative polymerase chain reaction pre-IC (cfEBV DNApreIC) and at IC completion. CfEBV DNApostIC was classified as undetectable (0 copy/ml) and detectable (>0 copy/ml). Recursive partitioning analysis (RPA) with respect to the overall survival (OS) was applied to construct a risk stratification system incorporating cfEBV DNApostIC and critical risk factors.
Results: We observed that 660 (72.5%) and 250 (27.5%) patients had cfEBV DNApostIC undetectable and detectable respectively. CfEBV DNApostIC positive was associated with a significant inferior 5-year OS (76.2% versus 85.9%), metastasis-free survival (DMFS, 71.7% versus 86.4%) and disease-free survival (DFS, 57.7% versus 80.1%) than cfEBV DNApostIC negative (P < 0.001 for all). Additionally, cfEBV DNApostIC was independently significant for OS (hazard ratio [HR] 1.90, 95% CI 1.40-2.59), DMFS (1.99, 1.45-2.71) and DFS (2.38, 1.86-3.06) in multivariate analyses (P < 0.001 for all). RPA modelling yielded three distinct risk groups: low-risk (N0-1 and undetectable cfEBV DNApostIC or N2-3 and pre-treatment cfEBV DNA [cfEBV DNApreIC] <7000), median-risk (N0-1 and detectable cfEBV DNApostIC or N2-3 and cfEBV DNApreIC ≥7000 with undetectable cfEBV DNApostIC) and high-risk (N2-3 and cfEBV DNApreIC ≥7000 with detectable cfEBV DNApostIC), with 5-year OS of 88.1%, 79.2% and 66.9%, respectively. Our risk stratification outperformed TNM classification for predicting death (AUC, 0.631 versus 0.562; P = 0.012) and distant metastasis (0.659 versus 0.562; P = 0.004).
Conclusions: CfEBV DNApostIC represents an effective indicator of prognostication in LA-NPC. We developed a risk classification system that provides improved OS prediction over the current staging system by combining cfEBV DNApostIC, cfEBV DNApreIC and N-stage classification in LA-NPC.
Keywords: Concurrent chemotherapy; EBV DNA; Nasopharyngeal carcinoma; Neoadjuvant chemotherapy; Targeted therapy; Treatment outcome.
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